Apparatus and method of intracranial imaging

ABSTRACT

The present invention provides an apparatus and method for detecting and predicting shape and underlying object properties. In accordance with an aspect of the present disclosure, there is provided an imaging apparatus having: an array of at least three co-planar electromagnetic transceiver defining a receiving plane; at least one deformable electromagnetic transceiver moveable orthogonally to the receiving plane; a two dimensional (2D) position tracking device configured to track a position of the electromagnetic transceiver on a surface 110 bounding a volume to be imaged; wherein the electromagnetic transceivers are configured to generate data from at least three depths below the surface for use in creating an image of the volume when the apparatus is moved along the surface.

FIELD

This application relates to methods, devices and apparatuses forimaging, particularly for tomographic imaging, more particularly fordetecting and imaging hematomas.

BACKGROUND

The standard of care for detecting and imaging hematomas in traumatichead injury is either computed tomography (CT) or magnetic resonanceimaging (MRI). Acute hematomas represent the largest cause of death fromhead injury, with a mortality rate of 50-60%. Mortality rate can belowered by diagnosis and treatment within the “golden hour” followingtraumatic head injury. However, CT and MRI are downstream technologiesemployed at large medical centers; accordingly, the time from injury todiagnosis is usually at least an hour, followed by subsequent treatmentoutside of the golden hour. A secondary concern is the increasing beliefthat the number of CT scans in general needs to be reduced, particularlyin pediatric populations, to reduce radiation exposure. Repeated CT isthe method of choice to monitor chronic hematoma, which is a common formof Traumatic Brain Injury (TBI) in the pediatric population.

There are also existing imaging technologies that utilize the NearInfra-Red (NIR) spectrum; examples are described in WO 2006/121833 andWO 2011/084480. The former is an older approach which cannot handle fullhead sampling and bilateral injuries; this is problematic, sinceapproximately 20% of hematomas are bilateral. The latter is a techniquewhich can provide rudimentary surface maps of hematomas; however, itlacks true 3D capabilities and further has no technology to ensure fullcoverage, relying purely on the training of the user to guaranteecoverage, which is a slow and subjective approach. Thus, the prior artNIR approaches have at least three deficits that need to be addressed:

-   -   1. Objective complete coverage by the untrained user. Neither of        the aforementioned prior art devices objectively guarantees that        full coverage can be obtained as in a CT/MRI.    -   2. Providing localization of the hematoma in the event of        extra-cranial bleeding. The aforementioned prior art provides a        ‘pseudo-volumetric image’ by comparing images acquired at two        depths; however, this approach fails in the presence of a        multi-layered event created by, for example, an extra-cranial        bleed. If (as is often the case) there is an extra-cranial bleed        associated with the intra-cranial hematoma, the extra-cranial        bleed induces absorption in the surface event at depth 1 and        will create uncertainty about the location and extent of the        intra-cranial bleed observed at depth 2.    -   3. Chronic monitoring. Chronic bleeds are often continuously        monitored to check for evolution of the bleed. With CT, there is        a balance between how often to image to ensure patient safety        vs. the radiation risks of multiple exposures. Although an NIR        device obviates the radiation risk and provides a better way to        study the evolution of a bleed, chronic monitoring is not        possible with the aforementioned technologies because only the        extent (2D) of the bleed can be monitored.

There is a need for new technology for early detection of hematomas.Such new technology would desirably permit rapid diagnosis, be portable(e.g. handheld), inexpensive, and capable of diagnosing acute injuriesas well as monitoring chronic injuries with reduced radiation exposureto patients as compared with conventional CT and MRI technologies. Itwould be further desirable that such new technology would permitvolumetric (3D) imaging in order to conduct full head sampling andobserve both hemispheres of the brain at the same time for bilateralhead injuries.

This background information is provided to reveal information believedby the applicant to be of possible relevance to the present disclosure.No admission is necessarily intended, nor should be construed, that anyof the preceding information constitutes prior art against the presentdisclosure.

BRIEF SUMMARY

An object of the present disclosure is to provide an apparatus andmethod for detecting and predicting shape and underlying objectproperties. In accordance with an aspect of the present disclosure,there is provided an imaging apparatus having: an array of at leastthree co-planar electromagnetic transceiver defining a receiving plane;at least one deformable electromagnetic transceiver moveableorthogonally to the receiving plane; a two dimensional (2D) positiontracking device configured to track a position of the electromagnetictransceiver on a surface bounding a volume to be imaged; wherein theelectromagnetic transceivers are configured to generate data from atleast three depths below the surface for use in creating an image of thevolume when the apparatus is moved along the surface.

In accordance with another aspect of the present disclosure, there isprovided an imaging apparatus for a curved surface having: an array ofat least three co-planar points defining a receiving plane; a twodimensional (2D) position tracking device configured to track a positionof the device on a surface bounding a volume to be imaged; and whereinthe apparatus is configured to measure the curved surface using apre-determined curved surface measuring means to measure deformation ofthe position tracking device.

accordance with yet another aspect of the present disclosure, there isprovided a method of intracranial imaging having: providing an imagingapparatus configured for movement along a surface of a cranium to beimaged, the imaging apparatus configured to generate data from at leastthree depths below the surface for use in creating an image of anintracranial volume; comparing the optical density of the at least threelayers to determine an optical density ratio between the layers; and,monitoring for changes in optical density ratio as a function of time ordistance moved by the imaging apparatus along the cranium.

In accordance with yet another aspect of the present disclosure, amethod of intracranial imaging having: providing an imaging apparatusmoving along at least three co-planar points defining a receiving plane,and implementing a two dimensional (2D) position tracking deviceconfigured to track a position of the device on a surface bounding avolume to be imaged, and wherein the apparatus is configured to measurethe curved surface using a pre-determined curved surface measuring meansto measure deformation of the position tracking device; comparing theoptical density ratio of the surface based on the curved surface meansto measure deformation; and monitoring for changes in optical densityratio as a function of time or distance moved by the imaging apparatusalong the cranium.

According to an aspect of the present disclosure, there is provided animaging apparatus comprising: an array of at least three co-planarelectromagnetic transceivers defining a receiving plane; at least onedeformable electromagnetic emitter moveable orthogonally to thereceiving plane; a two dimensional (2D) position tracking deviceconfigured to track a position of the electromagnetic emitter on asurface bounding a volume to be imaged; wherein the electromagneticemitter and transceivers are configured to generate data from at leastthree depths below the surface for use in creating an image of thevolume when the apparatus is moved along the surface.

The surface may be curved. In these instances a curved surface measuringmeans may be utilized for measurement of the curved surface. The curvedsurface measuring means may be implemented in a variety of ways as longas the method/mechanism allows for accurate measurement of the curvedsurface.

In at least one embodiment, the curved surface measuring means includeobtaining the image by continuously re- aligning the data from twodimensional (Cartesian) co-ordinates into curvilinear co-ordinates. Theapparatus may further comprise a first gyroscope and a second gyroscopespaced apart from the first gyroscope in a direction orthogonal to thereceiving plane by a known distance. The apparatus may further comprisesa displacement sensor configured to measure deformation of the at leastone deformable electromagnetic emitter moving on the surface. Theapparatus may further comprise a removable component containing at leastthe electromagnetic emitter and electromagnetic transceivers. Thispermits use of the apparatus with multiple interchangeable removablecomponents, each removable component comprising a different spacingbetween the electromagnetic transceivers and/or between theelectromagnetic transceivers and the electromagnetic emitter. In thecase of medical imaging, selection of a particular removable componentmay be based upon the age, gender or ethnicity of a subject beingimaged. The removable component may comprise an opaque exterior housing,with the electromagnetic transceivers and electromagnetic emitteroperable inside the housing. The electromagnetic emitter may comprise anoptical emitter (such as a near infra-red [NIR] emitter) and theelectromagnetic transceivers may comprise optical transceivers (such asNIR transceivers). The optical emitter may comprise a light emittingdiode (LED) and the optical transceivers may comprise light receivingdiodes (LRD) or avalanche photo-diodes (APD). The apparatus may beconfigured to utilize multiple optical wavelengths and may be configuredto utilize a temporal multiplexer and/or band pass filter to preventcontamination between the wavelengths.

In at least one embodiment, two or more gyroscopes are utilized forenhanced performance with respect to measuring a curved surface of asubject.

An imaging system according to the present disclosure may comprise animagine device as previously described interconnected with a computerconfigured to display a three- dimensional (3D) image of the volumebeing imaged.

The imaging apparatus as previously described may be used forintracranial imaging for the detection and/or monitoring of a sub-duralor epidural hematoma of a subject.

According to another aspect of the present disclosure, there is provideda method of intracranial imaging comprising: providing a near infra-red(NIR) imaging apparatus configured for movement along a surface of acranium to be imaged, the imaging apparatus configured to generate datafrom at least three depths below the surface for use in creating animage of an intracranial volume; comparing the optical density of the atleast three layers to determine an optical density ratio between thelayers; and, monitoring for changes in optical density ratio as afunction of time or distance moved by the imaging apparatus along thecranium.

The method may further comprise adjusting the number of layers beingimaged in response to a change in the optical density ratio. The methodmay further comprise adjusting the rate of movement of the imagingapparatus along the cranial surface in response to a change in theoptical density ratio. The method may further comprise comparingfeatures of the image with a brain atlas to obtain a registered imagelocation within the cranium. The method may further comprise creating apreferred path for the imaging device based on the registered imagelocation and the brain atlas. The method may further comprise placing ahead gear that is transparent to NIR electromagnetic radiation on thecranium and indicating the preferred path on the head gear. Thepreferred path may be indicated with reference to electromagneticreference signals of the head gear that interact with the imaging deviceto indicate its position on the head gear or by optically detectablereference indicia on the head gear.

The present disclosure provides advanced shape tracking and predictiveshape navigation with multi layered imaging capacity for real-timetomographic reconstruction of structural contrast. The presentdisclosure provides an approach to imaging that permits creation of truetomographic images with objectively guaranteed coverage. These shapeextraction and predictive tracking models have further applications to amultitude of medical technologies. They are especially relevant in thecurrent drive to the development of ‘tricorder like’ technologies.

The present disclosure is also useful for any implementation wheresurface reconstruction is required using a surface scanning technology,either purely for surface retrieval—with applications from art studies(e.g. contact shape and texture copying) to exploration technologies(e.g. wreck exploration)—or for any studying environment where scanningis occurring and the need to know the structure of the scan is importantas well the data scanned (e.g. scanning a pipeline for material defectsor damage).

The present disclosure is also useful for any volumetric imaging thatcan be achieved by some form of contrast imaging or ‘shadow casting’ canbe implemented with the present disclosure; for example, looking forimpurities in a neutron reactor. Predictive tracking is an even broaderarea of application. Some applications include: medical scanning fromsmall handheld technologies passed over the body ensuring objective fullcoverage; exploring a wreck remotely where, given a ship's layout, adrone could guide itself over the whole vessel checking the surface forweaknesses and stresses that may be risks to divers; remote surveying;tracking for exploring mineral deposits underground; space rovers and soforth.

The layered structural imaging in real time also has multiple uses inmedical imaging using NIR. Such uses include, for example, obtainingbetter models for any structural studies currently done usingsophisticated algorithms with static devices with limited sampling.These include, but are not limited to, stroke studies and breast cancerstudies. Uses may be extended to volumetric spectroscopic imaging atmultiple scales and multiple wavelengths.

One application of the technology is in the detection and imaging ofhematomas. The present disclosure is useful in acute and chronic, suband epidural hematoma detection and imaging for triage. The presentdisclosure uses multiple depths of sensory paths to recover a layeredstructural image of the medium. The present disclosure includes advancedmathematical techniques to capture shape and uses a priori atlases toguide and determine the path of tracking/measurement. An objectivedesign is provided to ensure coverage of the full head based on advancedshape tracking models and predictive motion guidance systems.

In another medical embodiment, the present disclosure may be used tomeasure concussions due to potential physiological changes induced inthe event. There is some suggestion that concussion induces a change inthe volume of cerebrospinal fluid. The present disclosure may be adaptedto detect near cranial surface changes in cerebrospinal fluid. As such,a concussion detection system may be provided.

Recent literature in the art has shown that near surface changes inthickness of the cerebro-spinal fluid relates to the presence of aconcussion. By using multiple NIR sensors over a known curvature we candetect the thickness and depth of the CSF by way of shape descriptorsobtained from the intensity profile across the surface. By tracking thisin motion across a known shape one may create a map of CSF thickness inthis region. This information will provide a map of the CSF beneath theskull, and will provide information on abnormal thickening which wouldindicate the presence of a concussion.

In another medical embodiment, biological markers have been identifiedwhose presence in the CSF indicate a negative response to the “return toplay” question. The absence of said markers allow for a “return to play”(or combat, or remove the flag for a state of heightened risk fromfurther head injury). It is possible to tag said markers using knownantibodies or affibodies tagged with an imaging marker. Such markerswould be detectable using such an apparatus and map-able over the head.

The use of multi-layered devices to address true volumetric as opposedto pseudo-volumetric images is a significant improvement over thetwo-layered device of WO 2011/084480. Further, the present disclosureabandons the requirement for multiple wavelengths without sacrificingutility, which is significant in an effort to simplify the technology toits basic need. This allows use of practically any NIR wavelength,thereby simplifying the detection system by making the detection systemwavelength independent.

The present disclosure may provide any one or more of the followingadvantages:

-   -   1. Objective complete coverage by the untrained user. The        present disclosure permits obtaining full coverage as in a        pre-existing structural image (e.g., CT and MRI, and the like),        where it is objectively guaranteed. With the new atlas guided        tracking system, an objectively guaranteed objective coverage        using a miniaturized scanning imaging device is provided.    -   2. Providing localization of the hematoma in the event of        extra-cranial bleeding. By applying a multi-layered model a        layered volumetric image may be recovered fully, allowing        discrimination of the possibility of an intracranial bleed        beneath an extra-cranial bleed. In order to acquire better        sensitivity and specificity the present disclosure adds extra        layers of information to provide higher sensitivity, with        specificity following from this.    -   3. Chronic monitoring. The use of multiple layers permits study        of the true 3D (extent and thickness) evolution of the bleed as        regularly as needed without irradiation risk. This is        significant since the depth information is important, providing        information about how much the hematoma is impinging on the        brain.    -   4. Further features will be described or will become apparent in        the course of the following detailed description. It should be        understood that each feature described herein may be utilized in        any combination with any one or more of the other described        features, and that each feature does not necessarily rely on the        presence of another feature except where evident to one of skill        in the art.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments of the present disclosure will be better understood inconnection with the following Figures, in which:

FIG. 1 schematically illustrates intended geometry of a tracking headfor a shape recovery/tracking sensor system for a device of the presentdisclosure in which the configuration is designed to achieve a fourpoint geometry intended to give a 3D reference position;

FIG. 2 schematically illustrates the concept of recovery of curvaturefrom a deformation applied to a shape recovery/tracking sensor systemfor a device of the present disclosure, where FIG. 2A illustrates theformation of a measured tetrahedral and FIG. 2B illustrates thecalculable fitted sphere constrained by the measured height;

FIG. 3 schematically illustrates use of two gyroscopes on a stemseparated by distance r with b being a distance delta r from a thirdmotion sensor (e.g. a surface tracker) in a shape recovery/trackingsensor system for a device of the present disclosure;

FIG. 4 schematically illustrates how to differentiate betweenextra-cranial and intra- cranial bleeds by identifying a skull/scalplayer between the two bleeds using extra penetration depths provided bya multi-layered NIR array sensor system in accordance with the presentdisclosure; and,

FIG. 5 schematically illustrates a multi-layered NIR array sensor systemfor a device in accordance with the present disclosure to implement thedifferentiation illustrated in FIG. 4.

DETAILED DESCRIPTION Definitions

The instant disclosure is most clearly understood with reference to thefollowing definitions:

Unilateral hematoma shall be understood to mean a hematoma inside thehead and in which blood collection or accumulation takes place on oneside of the head.

Bilateral hematoma shall be understood to mean a hematoma inside thehead and in which blood collection or accumulation takes place on bothsides of the head.

An epidural hematoma shall be understood to mean a hematoma inside thehead and where the blood collects or accumulates outside the brain andits fibrous covering (the Dura), but under the skull.

A subdural hematoma (SDH) shall be understood to mean a hematoma insidethe head and where the blood collects or accumulates between the brainand its Dura.

An intracerebral hematoma shall be understood to mean a hematoma insidethe head and where the blood collects or accumulates in the braintissue.

A subarachnoid hematoma or hemorrhage (SAH) shall be understood to meana hematoma inside the head and where the blood collects or accumulatesaround the surfaces of the brain, between the Dura and arachnoidmembranes. The term patient shall be understood to include mammaliansincluding human beings as well as other members of the animal kingdom.

An Extra Cranial Bleed shall refer to any accumulation of blood outsidethe cranium (skull) of the patient.

An Intra Cranial Bleed shall refer to any accumulation of blood insidethe cranium (skull) of the patient. It shall include, but not beexclusively: epidural, subdural, unilateral and bilateral hematomas,also included will be intracerebral hematomas.

An Acute Hematoma shall refer to the medical condition of a rapidlyevolving bleed requiring immediate treatment.

A Chronic Hematoma shall refer to the medical condition where thehematoma is small and evolving over time, requiring inpatient care andassessment over extended periods (multiple imaging cycles) to assesstreatment needs.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this present disclosure belongs.

Embodiments

Two primary embodiments are described herein, although the methods,devices and apparatuses described generally herein have a broad range ofapplications and lend themselves to many additional embodiments.Further, components of the present disclosure may be applied eitherindividually or as a whole to other applications.

In the first embodiment, a portable imaging device is provided fordetection of hematoma. This device uses a multi-layered (3 or more)model and circuitry and algorithms designed to discriminate differentdepths within the head and identify any ‘concealed intracranial bleed’.This device is provided in a version with a guidance system and aversion without a guidance system. The device may also include multipleinterchangeable detection heads to accommodate different skullthicknesses, which may vary according to age, race and gender.

In the second embodiment, an imaging device is provided and connectedwith a computing apparatus. In the second embodiment, a greater numberof layers are employed to create more complete volumetric images of thehematoma for use in, for example, research or surgical guidance. Thesecond embodiment may employ a portable imaging device according to thefirst embodiment as a detector that is equipped with an appropriatedetection head and interfaced by wireless or wired connection to thecomputer apparatus. Alternatively, the imaging device of the secondembodiment may be purpose built for greater sensitivity and/or field ofview. For chronic monitoring applications, the second embodiment mayinclude a stand, helmet or similar support structure to assist inpositioning the imaging device proximal to the patient's head for aprolonged period of time.

Decoupling Motion from Shape

The prior art in the field of shape reconstruction and remote sensingapplications (where an object's geometry is recovered) relies upon datacollected at a distance, using fixed position sensor readings obtainedfrom multiple sensors of known location applied to a static target. Inthe present disclosure, data must be collected from tracking pointsproximate a target using a single light source that is not at a fixedlocation, with the sensor placed upon a living target (i.e. potentiallymoving). This provides an entirely different problem. Current solutionsinvolve the use of fixed observation points monitoring the movingmeasurement device (stereotaxic imaging), or using a single gyroscopicmeasure to monitor the motion of the device and recover its path andorientation. These fall short if the target object is moving. Thisprovides a problem in terms of decoupling the motion of the devicecaused by the moving target from the spatial information collected asthe imaging device moves over the target.

The present disclosure employs two approaches to overcome theseproblems. The approaches are based upon the premise that, given asurface that is inherently 2D, a tracker (e.g. a mouse tracker) may beused to describe changes in location of the tracker on the surface;however the X-Y coordinate system will be non-unique and may bedistorted by curvature. Despite this, local differential changes may beexamined and converted to accurate surface translations if the localcurvature of the object is understood.

A first technique for accomplishing this is based on using twogyroscopes placed at known distances from the X-Y measure to permitdecoupling of the yaw of the device due to target shape from the yaw dueto target motion.

A second technique measures the deflection of a sensor caused by theshape of the object if it is mounted at a known point inside a fixedthree point geometry. This provides a known tetrahedron with a knownGreat sphere that will fit the four apexes. This provides a direct wayto measure shape change by decoupling the motion of the target from themeasurement.

Shape Recovery

Using standard algorithms, if the motion of an object is tracked in afixed 3D frame, the object's location and path may be described and ashape based on this trajectory may be generated. However, if the 3Dframe is also moving, it is more difficult to determine the object'spath and generate a shape, because it is difficult to separate motion ofthe object from motion of the tracking device. In one aspect of thepresent disclosure, an approach to handling this problem is provided. Itcan be shown mathematically that any closed surface object (or partthereof) is uniquely described by its surface normal and surfacelocation in 2D. To measure this, a device such as a mouse tracker isfirst used to acquire 2D lateralisation and continuously transformed asthe mouse travels based on the Jacobian of transformation tocontinuously realign these changes to the local differential changesbased on the surface topology or curvature change. Extracting thissimultaneously is important. In the first instance one could use asingle gyroscope, but this is susceptible to changes induced by themotion of the object and not the changes in the object itself. To avoidthis, the following approaches are used.

In at least one embodiment, by using a deformable device head (similarto a razor head) with three fixed contact points (forming a tripod), ameasurable, continuously variable deformation is created at the centreof this deformable surface. If the deformation is measured (by anymethod including, but not limited to, a laser rangefinder or a springbased deformation calibration) the local ‘Great Sphere’ generated bythis deformation may be extracted from trigonometric relations. Thisprovides the local curvature of the surface. As the device is moved andthe curvature changes, shape information is obtained which is completedby x-y tracking at the same location. This configuration is illustratedin FIG. 1 and FIG. 2. As stated above, the x-y data needs to berecalibrated to θφ (or similar curvilinear coordinates) based on theJacobian of transformation, as they are not equivalent to latitude andlongitude when measured using a conventional sensor. In at least oneembodiment, the utilization of a deformable device head comprises acurved surface measuring means.

Referring to FIG. 1 and FIG. 2, FIG. 1 illustrates the intended geometryof the tracking head. The configuration is designed to achieve a fourpoint geometry intended to give a 3D reference position. Three fixedpoints are given by the corners 100 of the device chassis, or by otherfixed structures incorporated in other embodiments. These form the baseof a tetrahedron that will be described below with reference to FIG. 2.The fourth point is a deformable sensor 110 that deforms orthogonally tothe plane of the three fixed points; in the current embodiment, theforth point is situated at the circumcenter of the triangle of points.This position is chosen solely for the ease of the mathematics and othernon-centrally located embodiments may also be used, but would requiremore extensive mathematical models to resolve the 3D shape.

FIG. 2A and FIG. 2B illustrate the concept of recovery of curvature froma deformation, where FIG. 2A shows the formation of a measuredtetrahedral and FIG. 2B shows the calculable fitted sphere constrainedby the measured height. FIG. 2A shows how a tetrahedron is formed whendeformable sensor 110 moves away from the plane created by fixed points200 at the corners 100 of the device chassis. The deformation gives thetetrahedron a measured height 220. The design of this is such that the‘largest sphere’ that sits on all points of the tetrahedron can bedetected, giving us a measure of curvature at deformable point 210,which is the location of the deformable sensor 110 out of the planedefined by the fixed points 200. FIG. 2B illustrates the great circle240 of the sphere passing through deformable point 210 and one apex ofthe triangle created by one of the fixed anchor points 200. If thetriangle is equilateral this is identical to all three points, makingthe math simpler, although other configurations are possible with morecomplex mathematics. In this instance we may derive from the geometry ofthe triangle and the height 220 of the tetrahedron the radius of thisgreat circle 240, equivalent to the radius of the sphere. This gives alocal measure of curvature. As the device is translated around, thiscurvature will change giving the local shape, along with a measure ofthe δx and δy provided by a collocated tracking device (either a mousetracker or similar). It is envisaged that the deformation sensor wouldwork off the ‘back’ of the motion tracking device, with zero being setas the depth of the tracking unit. Using spherical coordinates, or othermathematical corrections, δx and δy can be translated into angularcomponents of shift giving true surface motion. As the curvature isconstantly updated, the location may be modified based on the combineddata.

With reference to FIG. 3, in a second approach, two gyroscopes 390 and391 may be used at fixed positions (distances) from an x-y motiontracker 392. Using trigonometric relations it may be established thatthe two gyroscopes' movements come from the motion relative to a surface370 and the motion of the surface 370. By having the local distance oftravel, the vectors of translation may be computed and global movementmay be separated from local movement, thereby returning a shape. Achanging surface normal 6n is generated, which permits regeneration ofthe great circle, from where it is possible to proceed as outlinedabove. FIG. 3 illustrates the two gyroscopes 390 and 391 on a stemseparated by distance r along a tracking device axis 380 with gyroscope391 being a distance Sr from the x-y motion tracker 392 (e.g. a surfacetracker) along a deformable component 381 of the device axis 380. Thequantity of interest is the angular change in the gyroscope positions asa head of the motion tracker 392 moves in a yaw Y_(c). However a furtheryaw Y_(head) will be introduced by the motion of the head so the angularcomponent will have to be extracted from the relative yaws Y_(a) andY_(b) of the two fixed positions and the x-y component tracked by thedistance moved at the head. This may be done by assuming δr>>r andtherefore negligible, or by measuring it and giving a recursivealgorithm to eliminate Y_(head).

Shape Tracking (Prediction)

It is commonly known that one may register a volumetric image of anyindividual's head to an atlas head based on a variety of techniques. Itis in fact a much simpler task to map one surface to another, in asimilar way that image warping is achieved between two faces. If a shapeis being generated as the scanning device travels, as describedpreviously, the generated shape may then be mapped to a predicted atlasshape (e.g. a head, pipeline, room configuration). As trackingcontinues, an increased data (larger shape), is obtained, which permitsimprovement in the prediction of where the scanning device is located,in a similar fashion as a Kahlman filter. This is a novel approach toupdating registration based on partial data extraction. Having donethis, the position of the scanning device may be predicted, as it is nowpossible to register the image as it is taken and use this as a guide towhere the scanning device needs to go next, for example via a userinterface screen with an image of the atlas with a ‘tracking path’ on itshowing where the scanning device is and where it is traveling, leavingthe user then to ‘follow’ the path. Alternatively, in some remoteapplications, a guidance software and associated motor hardware areincluded to allow the device to move itself.

Layered Imaging

A layered image is generated by providing ratiometric measurements fromone depth to another. To achieve maximum accuracy, it is possible toprovide a set of measures by combining variation of ratios. For example,one could generate a simple (naive) image by comparing one depth to allothers. However, the present disclosure allows more sophisticated imagesto be generated by comparing each depth to its predecessor, or byskipping ‘n’ (where n is some number) depths. By using combinatoriallogic of different ratios, the best (sharpest) images are provided. Onemust further appreciate that ‘best’ will be application dependent, sothe methodology is described herein in its most generic form.

Specifically, in terms of targeting the extra-cranial bleeds anddetecting “hidden intra-cranial bleeds”, the sudden change in allchannels caused by an extra-cranial bleed allows the imaging device to‘switch mode’ from a simple approach of looking at the local vs. globalratios to including a quasi-local to local ratio based on the multipledepths as a normalising factor to detect the presence ofblood-skull-blood. The exact methodology may depend upon one or more ofrace, gender and age, due to the associated variation in skullthickness. This technique allows one to regenerate background averagesand determine the presence/absence of a non-blood layer sandwichedbetween the two blood layers based on ratiometric comparison.

The multi-layered principle of this device, in its simplestimplementation (3 sensory depths) is illustrated in FIG. 4. FIG. 4illustrates how, by probing multiple depths, layered structure may berecovered; for example, in the case of an extra-cranial bleedingcovering an intracranial injury. In the presence of an extracranialbleed 420, prior art methods and devices are unable to make decisivecomment on the presence of an intracranial bleed 440. For example, thedevice described in WO 2006-121833 will simply detect the presence orabsence of blood and the extracranial bleed will cause an automaticpositive. The device described in WO 2011/084480 will produce unknowndata and it will be unable to provide a definitive answer as to whetheror not the image is confounded by an extra-cranial bleed. In contrast,the device of the present disclosure uses at least 3 depths todifferentiate a multi-layered model, thereby permitting separation ofthe extra and intra cranial bleeds by identifying a skull/scalp layer430 between them using extra penetration depth or depths. NIR paths 450illustrated in FIG. 4 passing from a source 400 to each of detectors410,411,412 show clearly how differentiation is achieved. The number ofpaths and detectors may increase beyond three, depending on thepotential range of thicknesses of the extracranial bleed 420. Furtherembodiments of the device utilize more layers in order to see ‘beneath’the intracranial bleed 440 to provide thickness information in anevolving chronic hematoma.

Physical Aspects

A device of the present disclosure has two built in sensor systems, thefirst being a NIR array designed to assess the underlying tissuestructure, for example, and the second being a shape recovery/trackingsensor system. The former is illustrated in FIG. 4 from a functionalperspective. The latter is described in detail in FIGS. 1-3.

Physically, the device may employ a single light source (e.g. lightemitting diodes (LED)) and an array of detectors (e.g. light receivingdiodes (LRD) or avalanche photo diodes (APD)). With reference to FIG. 5,the device may be arranged such that light source 510 is placed near oneapex of a triangular head 530 of the device and then an array ofdetectors 500 (only four of fourteen labeled) are placed at knowndistances from the light source 510. In FIG. 5, four banks or rows ofdetectors 500 (one labeled in each row) are illustrated, each row ofdetectors initially providing one signal. However, in other embodimentsof the device the signals may be separated for advanced imagingtechniques. In FIG. 5, the rows are seen vertically and to the right ofthe light source 510 with two detectors in the first row, threedetectors in the second row, four detectors in the third row and fivedetectors in the fifth row.

The use of a laser mouse type motion tracker may lead to crosscontamination of the sensor data, so frequency multiplexing or the useof wavelength bandpass filters to separate the light based signals maybe necessary.

Given the successful layering as illustrated by FIG. 4, the question ofdepth penetration of the array must be considered in the presentdisclosure. In the prior art, the heads of the devices do not affect thegeometry of the sensor array in the device. In the present disclosure,interchangeable heads are designed specifically to adjust the geometryof the sensor array to make it age, gender and ethnicity specific. Inone embodiment, there are heads for two genders, two age groupings andpotentially 2 or 3 primary ethnicities. The idea of depth specificconfigurations, based on subject, is unique to the present device in theNIR literature. To achieve depth specific configurations, a flexible setof sources and detectors that return to a resting state are provided. Asthe detection head of the device is applied to the patient, it collectsdata from each source and detector and guides it to the correct locationbased on the age, gender and ethnicity of the subject for which thedetection head is designed. In one embodiment, the head is opticallytransparent at the setting for the source/detector, but elsewhere it isoptically opaque to prevent light leakage. Heads desirably aresterilizable or at least include a disposable sterilizable component dueto the potential of blood being present and the need for sterility ofthe device.

In an alternative embodiment, a diffuse optical device may be employedin which the detectors are interchangeable with the light source, andtemporal or frequency modulation is used to extract the different datachannels. Thus, a single detector may be used and the light sourcemultiplexed for measurement of different layers. This is especiallyuseful for devices for multiple layered measurements where the number ofdetectors would otherwise be too large for a portable device. Diffuseoptical strategies thus permit the construction of smaller, lessexpensive devices with less cumbersome electronics.

Method of Using a Device for Diagnosis

The aim is to minimise the number of potential detection heads. Thechoice of detection head may rely upon whether or not the patient isadult vs. child, male vs. female and then ethnicity. Ethnic measures ofskull thickness may indicate 2 possibly 3 different choices. It ispossible to remove the need for detection head selection by employinggreater separation distances (greater than 3). However, it may beimportant to have a head selection option available.

The device is applied to a head of the subject starting at a fixed point(above an ear for example). The user then spirals the device to coverthe whole of the subject's head to search for any possible injury. Thisprocess provides full head coverage. To ensure full head coverage, aguidance screen may be included that informs the user how to move thedevice. The guidance screen may involve any suitable type of screen, forexample an LCD screen (or similar) with a tracker path, a warning barthat shows the user whether they are following the prescribed path, or acombination thereof.

When used as an emergency diagnostic tool, the imaging apparatus mayhave an indicator light to inform the user that a hematoma is presentand that the patient's care should be prioritized accordingly. Thesecond embodiment involves the use of a secondary computer device(laptop or desktop), optionally with a wired connection, a wirelessconnection, or a bespoke docking unit. The computer runs software on thedata collected from the imaging device to provide an image of the headgiving the location of the bleed. In further embodiments, a plurality ofdetectors may provide a greater number and more advanced volumetricimages, providing not only information on where to drill to alleviatepressure but also the option to continuously monitor the evolution of achronic condition to allow for the determination of when surgicalintervention becomes necessary.

In the case of a priori known environments, for example in medicalimaging applications, a priori shape information about an object to bemeasured (e.g. the head of a subject) may be available to help ensurecoverage of the measuring operation and shape recovery from themeasurements made. In such cases, a suitable path could be pre-marked onthe object and the path may be tracked to ensure coverage and shaperecovery. However, it is challenging to correctly describe a suitablepath on an object and then to correctly follow the path with themeasuring device. To accomplish this, an inert shape fitting cover maybe applied to the object being measured and a surface path marked on thecover to provide a reference for determining the position of themeasuring device as it moves on the cover. A priori information from a“generic” shape of the object together with information provided aboutthe interaction of the measuring device with the cover provides positiontracking and shape reconstruction.

In one embodiment where a person's head is being scanned, an opticallyneutral head gear (e.g. a cap such as a ‘swim cap’ like attachment) maybe placed on the person's head and a suitable path “marked” on the headgear. This has the added advantage of providing extra sterility and easeof use of the measuring device. The path may be “marked” in a variety ofways.

In at least one embodiment, a set of RF transmitters may be embedded inthe head gear to permit continuous triangulation of the position of themeasuring device on the head gear during the measuring operation. Datafrom the RF transmitters may be stored in the measuring device andoutputted in the same manner as the optical data collected by themeasuring device.

A track marked as a bar code may be applied to the head gear and some‘image’ of the bar code may be stored while the measuring device is intransit. From the image of the bar code, the position of the measuringdevice along the track may be recovered at any time, thereby recoveringthe location of the measuring device.

A track with a raised tracking edge may be applied to the head gear andthe measuring device hooked to the head gear via the raised edge.Position of the measuring device may be provided from images of theraised track in a way similar to the bar code, and the raised track mayprovide a way to ensure continuous contact of the measuring device withthe person's head.

-   -   References: The contents of the entirety of each of which are        incorporated by this reference.    -   Ben Dor B, et al. (2006) System and Method for Detection of        Hematoma. International Patent Publication WO 2006-121833        published Nov. 16, 2006.    -   Riley J D, et al. (2011) Method for Detecting Hematoma, Portable        Detection and Discrimination Device and Related Systems and        Apparatuses.    -   International Patent Publication WO 2011/084480 published Jul.        14, 2011.

The novel features will become apparent to those of skill in the artupon examination of the description. It should be understood, however,that the scope of the claims should not be limited by the embodiments,but should be given the broadest interpretation consistent with thewording of the claims and the specification as a whole.

1. An imaging apparatus comprising: an array of at least three co-planarelectromagnetic transceivers defining a receiving plane; at least onedeformable electromagnetic transceivers moveable orthogonally to thereceiving plane; a two dimensional (2D) position tracking deviceconfigured to track a position of the electromagnetic transceiver on asurface bounding a volume to be imaged; wherein the electromagnetictransceivers are configured to generate data from at least three depthsbelow the surface for use in creating an image of the volume when theapparatus is moved along the surface.
 2. The apparatus according toclaim 1, wherein the surface is curved and wherein the image is obtainedby continuously realigning the data from two dimensional Cartesianco-ordinates into curvilinear co-ordinates.
 3. An imaging apparatus fora curved surface comprising: an array of at least three co-planar pointsdefining a receiving plane; a two dimensional (2D) position trackingdevice configured to track a position of the device on a surfacebounding a volume to be imaged; and wherein the apparatus is configuredto measure the curved surface using a predetermined curved surfacemeasuring means to measure deformation of the position tracking device.4. The apparatus according to claim 3, wherein the apparatus furthercomprises: a first gyroscope aligned with the two dimensional (2D)position tracking device; and a second gyroscope spaced apart from thefirst gyroscope in a direction orthogonal to the receiving plane by adistance.
 5. The apparatus according to claim 4, wherein one or moreadditional gyroscopes are implemented.
 6. The apparatus according toclaim 3, wherein the apparatus further comprises a displacement sensorconfigured to measure deformation of the two dimensional (2D) positiontracking device moving on the surface.
 7. The apparatus according toclaim 1, wherein the electromagnetic transceivers are opticaltransceivers.
 8. The apparatus according to claim 7, wherein the opticalemitter is a near infra-red (NIR) emitter and the optical receivers areNIR transceivers.
 9. The apparatus according to claim 7, wherein theoptical emitter comprises a light emitting diode (LED) and wherein theoptical receivers comprise a light receiving diode (LRD) or avalanchephoto-diode (APD).
 10. The apparatus according to claim 7, wherein theapparatus is configured to utilize multiple optical wavelengths.
 11. Theapparatus according to claim 10, wherein the apparatus is configured toutilize at least one of a temporal multiplexer, band pass filter, andfrequency multiplexer to prevent contamination between the multipleoptical wavelengths.
 12. The apparatus according to claim 1, furthercomprising an imaging system interconnected with a computer configuredto display a three-dimensional (3D) image of the volume.
 13. Theapparatus according to claim 1, wherein the apparatus is configured forthe detection and monitoring of a hematoma and/or a concussion of asubject.
 14. (canceled)
 15. A method of intracranial imaging comprising:providing an imaging apparatus configured for movement along a surfaceof a cranium to be imaged, the imaging apparatus configured to generatedata from at least three depths below the surface for use in creating animage of an intracranial volume; comparing the optical density of the atleast three depths to determine an optical density ratio between thedepths; and monitoring for changes in optical density ratio as afunction of time or distance moved by the imaging apparatus along thecranium.
 16. The method according to claim 15, wherein the methodfurther comprises adjusting the number of layers being imaged and/or therate of movement of the imaging apparatus along the cranial surface inresponse to a change in the optical density ratio.
 17. (canceled) 18.The method according to claim 15, wherein the method further comprisescomparing features of the image with a pre-existing structural image toobtain a registered image location within the cranium, wherein thepreexisting structural image comprises at least one of: a brain atlasand MRI.
 19. The method according to claim 18, wherein the methodfurther comprises creating a preferred path for the imaging device basedon the registered image location and the preexisting structural image.20. (canceled)
 21. The method according to claim 19, wherein the methodfurther comprises placing a head gear that is transparent to NIRelectromagnetic radiation on the cranium and indicating the preferredpath on the head gear.
 22. The method according to claim 21, wherein thepreferred path is indicated with reference to electromagnetic referencesignals of the head gear that interact with the imaging apparatus toindicate its position on the head gear or by optically detectablereference indicia on the head gear.
 23. The method according to claim15, wherein the imaging apparatus comprises a transceiver which is anear infra-red (NIR) transceiver and an optical transceiver.
 24. Themethod according to claim 15, wherein the imaging apparatus isconfigured for the detection and monitoring of a hematoma and/or aconcussion of a subject.
 25. A method of intracranial imagingcomprising: providing an imaging apparatus moving along at least threeco-planar points defining a receiving plane, and implementing a twodimensional (2D) position tracking device configured to track a positionof the device on a surface bounding a volume to be imaged, and whereinthe apparatus is configured to measure the curved surface using apre-determined curved surface measuring means to measure deformation ofthe position tracking device; comparing the optical density ratio of thesurface based on the curved surface means to measure deformation; andmonitoring for changes in optical density ratio as a function of time ordistance moved by the imaging apparatus along the cranium.
 26. Themethod of claim 25, wherein the surface measuring means comprises atleast one of the following: one or more gyroscopes and a displacementsensor.
 27. The method of claim 25, wherein the imaging apparatusfurther comprises: a first gyroscope aligned with the two dimensional(2D) position tracking device; and a second gyroscope spaced apart fromthe first gyroscope in a direction orthogonal to the receiving plane bya distance.
 28. The method of according to claim 27, wherein the imagingapparatus further comprises one or more additional gyroscopes.
 29. Theapparatus according to claim 25, wherein the imaging apparatus furthercomprises a displacement sensor configured to measure deformation of thetwo dimensional (2D) position tracking device moving on the surface. 30.The method according to claim 25, wherein the imaging apparatus isconfiqured for the detection and monitoring of a hematoma and/or aconcussion of a subject.